Task failed: P2VError UFAD_SYSTEM_ERROR(Invalid response code: 400 Bad Request)

VMware Converterでlogに上記エラー(GUIはERROR: VMware Converter Agent System Error)が出ていた件はvmx等に日本語が使われていたのが原因のようだ。
http://communities.vmware.com/thread/119447

This issue is due to the ASCII to UTF-8 string conversion in the following fields:

 * Annotation
 * Display name
 * Floppy image name
 * Parallel port file name
 * Serial port file name
 * CDROM iso name

These fields are may not contain any non standard Engish ASCII characters. (Any other than ASCII 33-127)

WSデフォルトのクローン時の名称に日本語が使われるのは良し悪しだな。